Influence of 5,10-methylenetetrahydrofolate reductase gene polymorphism on plasma homocysteine concentration in patients with end-stage renal disease

The purpose of this study is to observe the influence of the methylenetetrahydrofolate reductase (MTHFR) gene (677C-->T substitution) on plasma homocysteine levels in end-stage renal disease (ESRD) patients who received a relatively large amount of folate (2 mg/d) and are undergoing hemodialysis. A cross-sectional study of plasma homocysteine, vitamin B(12), and folate was performed in patients with ESRD. The study population for the MTHFR gene study included 312 healthy subjects and 106 patients with ESRD undergoing hemodialysis. The C677T transition in the MTHFR gene was detected by HinF 1 restriction enzyme analysis and subsequent electrophoresis in a 3% agarose gel. The genotype of the MTHFR gene in 106 patients with ESRD was homozygous C677T mutation (VV) in 17 patients (16.1%) and heterozygous (AV) in 63 patients (58.4%); 26 patients (24.5%) did not carry this mutation (AA). The mean levels of homocysteine, vitamin B(12), and folate in the patients with ESRD were 23.3 +/- 14.0 mmol/L, 620.2 +/- 98.5 pmol/L, and 138.6 +/- 55.6 nmol/L, respectively. There was no significant difference in homocysteine levels among the three genotypes: 28.2 +/- 19.4 mmol/L for VV, 22.7 +/- 14.9 mmol/L for AV, and 23.4 +/- 11.1 mmol/L for AA genotype (P > 0.05). There was no difference in genotype distribution between the patient groups of less than 25th and greater than 75th percentiles, classified according to plasma homocysteine levels (P = 0.47). In conclusion, with high-dose folate supplementation, the hyperhomocysteinemia in patients with ESRD does not seem to be caused by the 677C-->T mutation in the MTHFR gene.

Molecular modeling of hapten structure and relevance to broad specificity immunoassay of sulfonamide antibiotics

Molecular modeling of hapten structure was used to predict and influence, through appropriate synthetic work, the outcome of an immunization program. Examination of the structures of sulfonamide antibiotics led to the development of a hypothesis and the consequent synthesis of a sulfacetamide-protein immunogen aimed at the generation of broad specificity anti-sulfonamide antibodies. The antisera generated, alongside anti-sulfachlorpyradizine antisera generated at the same time, were characterized for cross-reactions against a range of sulfonamide drugs, and were found to exhibit good but not the desired broad specificity. Discussion is presented as to the reasons for the failure of the hypothesis. Further hypotheses are developed and speculation is made as to the future of molecular modeling in immunochemical research.

Influenza A virus RNA polymerase has the ability to stutter at the polyadenylation site of a viral RNA template during RNA replication

The viral polymerase of influenza virus, a negative-strand RNA virus, is believed to polyadenylate the mRNAs by stuttering at a stretch of five to seven uridine residues which are located close to the 5' ends of the viral RNA templates. However, a mechanism of polyadenylation based on a template-independent synthesis of the poly(A) tail has not been excluded. In this report, we present new evidence showing the inherent ability of the viral polymerase to stutter at the poly(U) stretch of a viral RNA template during RNA replication. Variants which possess 1- to 13-nucleotide-long insertions at the poly(U) stretch have been identified. These results support a stuttering mechanism for the polyadenylation of influenza virus mRNAs.

Monoclonal anti-idiotype antibody mimicking the pesticide binding site of cutinase: potential for broad specificity organophosphate recognition

An anti-idiotype monoclonal antibody (Mab) able to bind the organophosphate pesticides, chlorfenvinphos (CFV), ethyl paraoxon, tetrachlorfenvinphos and demeton-s-methyl, has been produced using as immunogen a Mab which binds to the active site of cutinase. The principle of using an anti-idiotype antibody as the mimic of a site on a protein able to bind a group of ligands has, therefore, been demonstrated, and may have implications for future research on broad specificity immunoanalysis of groups of compounds.

L-carnitine and acetyl-L-carnitine status during hemodialysis with acetate in humans: a kinetic analysis

The effects of the acetate content of hemodialysis fluids on the relation between L-carnitine (free carnitine, cr FC) and acetyl-L-carnitine (AC) have not previously been examined in detail. The net fluxes of FC, AC, and acetate between intra- and extracellular pools during hemodialysis were calculated using a kinetic model with dialysates containing three concentrations of FC (0, 40, and 80 mumol/L) and either 40 or 3 mmol acetate/L. Radioenzymatic assays of FC and AC were optimized for use with samples taken during hemodialysis. Acetate stimulated a tissue uptake of FC (P < 0.05) that could exceed the rate of FC delivery and was related to the dialysate FC composition (P < 0.02). There were associated changes in tissue AC output. With dialysate containing 40 mmol acetate/L, AC tissue output was directly related to the dialysate FC composition (P < 0.05). The AC tissue output was less with dialysate containing 3 mmol acetate/L (P < 0.05) but the significant increase with the provision of FC in the dialysate was retained (P < 0.05). Hemodialysis may therefore represent an acute period of relative carnitine deficiency when regeneration of free coenzyme A from acetyl coenzyme A consequent to metabolism of acetate is limited.

Surface ultrastructures of the third-stage larvae of Gnathostoma hispidum

A scanning electron microscopic study was performed to observe the surface ultrastructures of the third-stage larvae of Gnathostoma hispidum. The early third-stage larvae (EL3) were collected from the viscera of Chinese loaches by the artificial digestion method. The advanced third-stage larvae (ADL3) were recovered from mice experimentally infected with EL3. Both larval worms were fixed with 2.5% glutaraldehyde, dehydrated in graded alcohol, dryed in critical point dryer, and coated with gold. The specimens were observed with a SEM (DS-130C). On the head bulb of both larval stage, the mouth had a pair of lateral lips of equal size and of half moon shape. Each lip had a couple of labial papillae and a small amphid located between the two papillae. The hooklets on the head bulb had single-pointed tips and curved posteriorly. The cuticular spines of EL3 were larger and more densely distributed in the anterior area (about 1.8 micron in length) and gradually decreased in size and number posteriorly. The cuticular spines in the anterior area of ADL3 were sharp-pointed and about 4.5 micron in length, and those in the middle area were about 1.75 micron. The velvety cuticular folds and dot-like cuticular spines were distributed in the posterior area. A cervical papilla was located between the 7th and 8th transverse striations. A dome-like body papilla was located at the posterior 1/4 of body. An ellipsoidal excretory pore was located between the 17th and 18th striations. From the above results, it is suggested that the characteristic SEM findings obtained from this study may be helpful on the species identification of larval Gnathostoma.

Serum C-reactive protein. A useful and economical marker of immune activation in renal transplantation

This study investigated whether serial daily measurements of serum C-reactive protein (sCRP) in 187 renal allograft recipients could help discriminate episodes of renal dysfunction due to rejection or cyclosporine (CsA) nephrotoxicity and help adjust immunosuppression in the early posttransplant period. Excellent primary graft function was associated with an initial peak of sCRP on day 2 after transplant (median, 29 microg/ml; range, 4 to >200 microg/ml) with a return to <20 microg/ml in all patients by day 5 (median, 7 microg/ml; range, 2-19 microg/ml). Stable graft function (mean creatinine, 155 microg/ml) was accompanied by a median sCRP of 4 microg/ml (range, 1-19 microg/ml). In 30 episodes of rejection responsive to methylprednisolone, sCRP was initially significantly raised to a median of 49 microg/ml (P<0.001) but fell rapidly in response to treatment to a median of 11 microg/ml and continued to fall. In 19 episodes of rejection unresponsive to methylprednisolone, median initial sCRP levels were significantly higher (P<0.001) at 119 microg/ml and were still at a median of 77 microg/ml at the end of the treatment. Twenty-four patients in whom renal dysfunction was associated with CsA nephrotoxicity showed no increase in sCRP concentrations; median sCRP concentrations remained at <5 microg/ml throughout the episodes. A similar pattern was seen in patients with acute tubular necrosis. Serial sCRP measurements provide economical and reproducible evidence of immune activation, help discriminate renal dysfunction due to CsA nephrotoxicity or rejection, and allow appropriate modification of immunosuppressive therapy.

Comparison of a microtitration plate ELISA with a standard cultural procedure for the detection of Salmonella spp. in chicken

A rapid antibody-capture enzyme-linked immunosorbent assay (ELISA) detecting a wide range of Salmonella serotypes and employing only one culture stage was used to analyze the giblets and body cavity rinsings from frozen chickens. The results from the ELISA were compared with those obtained using a standard cultural procedure in current use in two laboratories, Norwich (N) and Ipswich (I), of the Public Health Laboratory Service (PHLS) in the UK. ELISAs were carried out on the same samples at each of two PHLS laboratories and at the Institute of Food Research with good agreement (94% and 90%). When compared with the cultural method there was 80% and 70% agreement with the ELISA with the PHLS(N) and PHLS(I) samples. The ELISA appeared to have a false-positive rate of 17% (samples from PHLS(N)) but on reculture of the "negative" samples this rate fell to 7%. The false-negative rate for the ELISA was 26% (samples from PHLS(N)) which appeared to be due to insufficient growth of the Salmonella spp. in the single cultural step employed in the ELISA rather than lack of recognition by the antibodies. The problem of false negatives with the cultural method is also discussed. These results are comparable to previously published studies relating immunoassays and the conventional procedure for Salmonella detection when analyzing similar samples. Suggestions are made as to how further increases in ELISA efficiency might be brought about.

Plasma non-esterified fatty acid response to dialysate acetate concentration during haemodialysis in humans

We have inhibited the in vitro generation of non-esterified fatty acids in plasma samples taken during haemodialysis by cooling the samples rapidly, centrifuging and freezing within 5 min of sampling and completing the assay on the same day. The relationship of non-esterified fatty acid concentrations during haemodialysis to the acetate concentration of the dialysate and the profile of circulating lipase activities was studied. With this sample-handling protocol we found lower non-esterified fatty acid concentrations than reported in many other studies and the results suggest that, under normal conditions of haemodialysis, the circulating non-esterified fatty acid concentrations and the associated risk of unwanted side-effects may have been previously over-estimated due to artefactual in vitro sample lipolysis. We also showed that, at the end of dialysis, when circulating lipase activities were least, the non-esterified fatty acid concentrations were lower (P < 0.05) with an acetate dialysate containing 37 mmol/l acetate than with a bicarbonate dialysate containing 3 mmol/l acetate.

Severe hyponatraemia in a quadriplegic

A young quadriplegic patient developed convulsions and brain damage due to severe hyponatraemia. Potential causes of severe hyponatraemia in quadriplegics include excessive water intake (because of the low threshold for vasopressin release) and asymptomatic renal tract infection causing sodium loss. Mild hyponatraemia, occurring in up to 10% of quadriplegics, is due to a reset osmostat.

Combined 17 alpha-hydroxylase/17,20-lyase deficiency caused by heterozygous stop codons in the cytochrome P450 17 alpha-hydroxylase gene

OBJECTIVE

To determine the genetic defect underlying congenital adrenal hyperplasia due to 17 alpha-hydroxylase deficiency in a genetic female.

DESIGN

Blood samples were used as a source of genomic DNA. A library of size selected genomic DNA sequences was prepared. In addition, portions of the 17 alpha-hydroxylase gene were amplified by the polymerase chain reaction and the gene products sequenced.

PATIENTS

Samples were obtained from a patient with sexual infantilism, lack of secondary sexual characteristics and hypertension. Streak gonads were found on laparoscopy.

RESULTS

Two point mutations were found, one in exon 3 and one in exon 4 which generate premature stop codons at codons 194 and 239 in place of glutamate and arginine respectively. The mutation in exon 3 has not previously been reported in patients with 17 alpha-hydroxylase deficiency.

CONCLUSION

The protein product of these defective genes could be expected to be severely truncated with no catalytic activity. This is in keeping with the complete lack of cortisol and sex steroid output in this patient. The polymerase chain reaction provides faster access to gene sequence information than previous procedures based on library screening prior to sequencing.

Further studies on the feasibility of one-day Salmonella detection by enzyme-linked immunosorbent assay

A model system previously developed for the rapid detection of Salmonella typhimurium in foods was improved and extended to many other Salmonella serotypes. The original protocol, which consisted of an overnight nonselective culture followed by a specific enzyme-linked immunosorbent assay (ELISA), was modified and improved. A sandwich ELISA which used polyclonal antibodies for the capture stage and a cocktail of monoclonal antibodies for the detector stage was developed. The assay recognized a wide range of Salmonella serotypes; S. enteritidis, the most important serotype in the United Kingdom had a detection limit in the ELISA of about 4 x 10(2) cells ml-1. The cultural stage prior to the ELISA was either a single nonselective broth (incubated for 28 h) or a preenrichment broth (incubated for 7 h) plus a selective broth (incubated for 21 h). Antibodies which bind to cells grown in the unfavorable conditions of a selective medium were selected. It was concluded that, in the future, the shortened protocols for the detection of Salmonella spp. in foods described here will be of considerable value.

Milk-alkali syndrome due to Caved-S

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Lack of correlation between IgG T-lymphocyte flow cytometric crossmatches with primary renal allograft outcome

The flow cytometric crossmatch (FCXM) has been reported to be more sensitive and capable of detecting very low levels of antibodies than the normally used complement dependent cytotoxicity test. We studied both the two colour IgG T cell FCXM and CDC-XM in 146 renal allograft recipients, 111 primary and 35 regrafts, of which 26% (29/111) of 1st and 20% (7/35) of regrafts had a positive FCXM. There was no overall correlation between the FCXM results and early graft outcome in primary renal allografts. The FCXM did not appear to have any advantage over the CDC-XM in predicting graft outcome in unsensitized first grafts. In the small number of regrafts studied, a positive FCXM was associated with a higher degree of graft failure. FCXM can exhibit false negative results if sera are used solely neat although these prozone phenomena do not influence subsequent graft outcome.

Uraemia: is urea more important than we think?

Urea is accumulated as an osmolyte by some groups of animals even though it impairs protein function. These organisms can withstand high internal urea concentrations because they also accumulate other low-molecular-weight osmolytes, the methylamines, which can offset the effects of urea on proteins. Methylamines have also been found in the medulla of the mammalian kidney (where urea concentrations are high) and in the plasma of human subjects with chronic renal failure. These findings suggest that previous investigations of the potential contribution of urea to the syndrome of uraemia may have been confounded because of the presence of variable concentrations of protective substances. That naturally occurring methylamines or related substances may prove to have a useful therapeutic role in uraemia is also possible.

Bartter's syndrome and diabetes mellitus

We here report a case of Bartter's syndrome occurring in association with diabetes mellitus. The patient, an insulin-dependent diabetic, presented with hypokalaemia, inappropriate kaliuresis and metabolic alkalosis. He had high plasma renin activity, relatively low plasma aldosterone, and resistance to infused angiotensin II. A high potassium diet raised total body potassium and serum potassium, did not affect plasma renin activity, but raised plasma aldosterone significantly and did not alter the resistance to angiotensin II. Indomethacin administered acutely reduced urinary potassium and kallikrein excretion and, on chronic administration, lowered plasma renin activity, urinary chloride excretion, and raised serum potassium. Salt restriction resulted in a prompt and significant reduction in urinary sodium and chloride excretion. Urinary kallikrein excretion was very high throughout, increased with sodium restriction, and decreased with sodium loading. Oral potassium supplementation partially corrected the hypokalaemia, but did not affect blood sugar control. In this patient the primary defect appears to have been primary urinary potassium wasting, rather than sodium or chloride wasting. The striking effects of indomethacin suggest that prostaglandins may play a fundamental role in the genesis of the syndrome.